With the progress of virtualization techniques of computer resources, it becomes possible to operate multiple virtual computers on one computer (refer to the non-patent document 1).
Also, development of a technique called live migration is under way to transfer a system operating as a virtual computer to another computer on a certain physical computer without stopping the system (refer to the non-patent document 2).
In addition, development of a technique for virtualizing a network is under way (refer to the non-patent document 3), so that it is possible to construct a plurality of virtual networks on a single physical network.
Discussion is being made on a method of embedding virtual nodes and a virtual network connecting between virtual nodes by using network resources and computers held by a network operator (to be referred to as a infra provider hereinafter) that maintains and manages physical networks by utilizing these techniques (refer to non-patent document 4). In this discussion, a virtual network operator that controls the virtual network arranges necessary virtual nodes and virtual resources to construct the virtual network in order to meet requests from a service provider that actually provides network services. Then, the constructed virtual network is provided to the service provider, so that services of the service provider are provided using the virtual network.
In this environment, resources required by each virtual network momentarily change due to change of demand and the like for services provided by service providers. Also, the number of virtual networks that need to be embedded changes over time, in which, for example, it becomes necessary to embed a new virtual network when launching a new service, or a virtual network becomes unnecessary as a service ends. For such an environmental change, a method for reconstructing an already embedded virtual network has been discussed (refer to non-patent document 5).